ABSTRACT Hidradenitis suppurativa (HS) is an important inflammatory disease, which affects approximately 1% of adults, and causes painful nodules, draining abscesses, and disfiguring scars that make walking, sitting, and working difficult or impossible. Progress to investigate HS is impeded by the lack of comprehensive outcome measures for use in trials and clinical care. Existing HS-specific disease severity tools are limited because signs of disease damage, such as discoloration and scarring, are either not captured or incorporated into a single score. In addition, some tools are impractical or not validated, reliable, or responsive. A disease-specific patient-reported outcome measure does not exist and given the impact of HS on patient well-being, it is vital to engage patients in outcome measurement. The goal of this proposal is to develop HS-specific measures to support accurate disease assessment. The specific aims of the proposed research are: (1) to test the hypothesis that a novel HS-specific patient-reported outcome measure will have substantial validity, reliability and responsiveness; (2) to test the hypothesis that a new provider-reported disease severity measure will have substantial validity, reliability and responsiveness. Patients with HS, age 18 or older, will be recruited from the PaTH network, an integrated clinical data research network across four Mid-Atlantic health systems, Penn State Hershey Medical Center, University of Pittsburgh Medical Center, Johns Hopkins Medical Center, and Temple Health System. The patients in the PaTH network are diverse; over 25% are non-white; 20% have public insurance or no insurance. The development and validation process will be based on the NIH PROMIS Instrument Development and Validation Scientific Standards. Briefly, we will include stakeholders, patients and providers, in the development and refinement of the tools. We will rigorously test the psychometric and measurement properties, including the reliability and validity, with the input of patients and providers. Finally, we will focus on evaluating the responsiveness of these novel patient- and clinician-reported outcome measures for HS.